In these days, and primarily in the industrialized countries, there is a deep concern about the safe disposal of domestic and industrial wastes which have acquired great ecological importance. These wastes often include a substantial proportion of organic content.
Many such wastes often contain toxic substances and are nonbiodegradable. They cannot therefore simply be disposed of in landfills due to contamination problems of air and water. Another alternative to dispose of these wastes is incineration. Normal and simple incineration however is not permitted if the product gases are not duly cleaned because it causes air pollution with toxic chemicals for example, chlorine compounds and nitrogen oxides. In some countries, environmental laws and regulations have been passed which prohibit burial or incineration of these types of wastes. Therefore these alternatives for disposal of such wastes are now subject to many restrictions.
A thorough description of the problems which the shredding industry is facing regarding disposal of fluff and some suggestions for utilization of the energy content of fluff, is found in a paper by M. R. Wolman, W. S. Hubble, I. G. Most and S. L. Natof, presented at the National Waste Processing Conference in Denver, Colo. held on Jun. 14, 1986, and published by ASME in the proceedings of said conference. This paper reports an investigation funded by the U.S. Department of Energy to develop a viable process to utilize the energy content of fluff. However, the process therein suggested is aimed to carry out a total incineration of the wastes, utilizing the heat from said incineration for steam production, while the present invention is addressed to producing from organic materials a high quality gas as an energy source.
It has also been proposed in the past to carry out a controlled combustion of the organic wastes and to utilize the heat or other values (such as process gases) released by such combustion. Such prior art processes typically gasify organic materials by one of two processes: pyrolysis, that is, thermal decomposition of the materials by indirect heating; or partial combustion of the materials with air or oxygen.
Energy consumption is one of the most important costs in ironmaking. Typical direct reduction processes consume from 2.5 to 3.5 Gigacalories (109 calories) per metric ton of product, known as sponge iron or direct reduced iron (DRI). Therefore, many processes have been proposed which utilize all types of available energy sources, such as coal, coke, liquid fuels, natural gas, reducing gases from biomass, nuclear energy and solar energy. Most of such proposals have not met practical success, sometimes because the materials and means needed are not yet available or because the relative costs for using such other energy sources are higher than for traditional fossil fuels.
Utilization of organic wastes as a source of energy for the ironmaking industry offers great economic advantages and solves environmental problems in those countries where large quantities of automobiles are scrapped or other wastes with high organic material content are generated. Metallic scrap is recycled for steelmaking. The nonmetallic residues of automobiles (fluff), however, had not been utilized to produce reducing gases useful in the production of iron or in other industrial processes.